Punctuation that precedes or immediately follows the first letter is included in the match. Punctuation includes any Unicode character defined in the open (Ps), close (Pe), initial quote (Pi), final quote (Pf), and other punctuation (Po) classes.

Some languages have digraphs that are always capitalized together, like the IJ in Dutch. In these cases, both letters of the digraph should be matched by the ::first-letter pseudo-element. (This is poorly supported by browsers; see the browser compatibility table below.)

A combination of the ::before pseudo-element and the content property may inject some text at the beginning of the element. In that case, ::first-letter will match the first letter of this generated content.

CSS3 introduced the ::first-letter notation (with two colons) to distinguish pseudo-classes from pseudo-elements. Browsers also accept :first-letter, introduced in CSS2.

Allowable properties

Only a small subset of CSS properties can be used with the ::first-letter pseudo-element: